Controlling LED's Using Ultrasonic Distance Sensor

1#define Trigpin 7
2#define Echopin 8
3#define low_led 9
4#define  high_led 10
5float distance;
6int duration;
7int ll = 700;
8
9void setup()  {
10  pinMode (Trigpin, OUTPUT);
11  pinMode (low_led, OUTPUT);
12  pinMode (high_led,  OUTPUT);
13  pinMode (Echopin, INPUT);
14  Serial.begin(9600);
15  Serial.println  ("Welcome To Distance Meter");
16  Serial.println ("Coded By Jevins Annson");
17  digitalWrite (low_led, LOW);
18  digitalWrite (high_led, LOW);
19}
20
21void  loop() {
22  digitalWrite(Trigpin, LOW);
23  delayMicroseconds(2);
24  digitalWrite(Trigpin,  HIGH);
25  delayMicroseconds(10);
26  digitalWrite(Trigpin, LOW);
27  duration  = pulseIn(Echopin, HIGH);
28  distance = duration * 0.034 / 2;
29  delay (ll);
30  Serial.println (" ");
31  Serial.print ("Distance = ");
32  Serial.print  (distance);
33  Serial.print (" CM");
34  Serial.println (" ");
35
36  if  (distance>=30)
37  {
38    Serial.println ("Nobody Is Infront Of the Sensor");
39    digitalWrite (low_led, HIGH);
40    delay (500);
41    digitalWrite (low_led,  LOW);
42    delay (500);
43    digitalWrite (low_led, HIGH);
44  }
45  else  
46  {
47    Serial.println ("Someone Is Infront Of the Sensor");
48    digitalWrite  (high_led, HIGH);
49    delay (100);
50    digitalWrite (high_led, LOW);
51    delay  (100);
52    digitalWrite (high_led, HIGH);
53    delay (100);
54  }
55}
56